L-carnitine: energy metabolism is real, fat-loss claims are mixed

## What is it? L-carnitine is an amino-acid-derived molecule involved in moving long-chain fatty acids into mitochondria. It is not a peptide. Healthy adults generally make enough carnitine; treatment of a diagnosed deficiency is a different clinical question from performance or weight-management use. [1]

## What do studies show? The NIH Office of Dietary Supplements reports mixed results from oral L-carnitine exercise studies, with no consistent performance advantage. Weight-loss trials are also mixed: one trial combining oral carnitine with orlistat found a larger loss than orlistat alone, while another using oral carnitine alone found no weight-loss effect. A meta-analysis found a modest average difference, but larger studies are needed. These findings do not show that a research injection vial causes fat loss. [1]

## Safety Supplement amounts around 3 g/day can cause gastrointestinal symptoms and a fishy body odor. Caution is also noted for people with seizure disorders and certain medication use. Injectable formulations introduce different quality and route questions; evidence from oral supplements cannot settle those. [1]

## How much? Studied oral supplement amounts have commonly been about 1–4 g/day, depending on the trial and outcome. That is a study range, not a recommended dose for everyone, and cannot be converted into an injection schedule for a catalog vial. A clinician should select treatment for a diagnosed carnitine deficiency; no standard fitness-injection dose is established here. [1]